Banding and balancing of dynamo-electric machines



H. WACLAW 3,

BANDING AND BALANCING OF DYNAMOELECTRIC MACHINES April 4, 1967 2 Sheets-Sheet 1 Filed June 24, 1964 HENRI WACLAW INVENTOR BY WQZWATTORNEY April 1967 HQWACLAW 3,312,847

BANDING'AND BALANCING OF DYNAMOELECTRIC MACHINES Filed June 24, 1964 2 Sheets-Sheet 2 FIG. 5

HENRI WACLAW INVENTOR BY I l KWTTORNQ United States Patent Jersey Filed June 24, 1964, Ser. No. 377,719 16 Claims. (Cl. 310-271) This invention relates generally to rotors for dynamoelectric machines and particularly to a method and means for handing the end turns thereof and simultaneously facilitating the addition of balancing weights thereto.

In the manufacture of wound rotors for dynamoelectric machines, particularly direct current machines, it is usually necessary to provide some kind of band around the end turns to resist the action of centrifugal force. Also, it is usually necessary to balance each rotor dynamically by adding weights of such size and at such locations as are determined by testing in a balancing machine.

One common construction comprises applying a layer of insulation, such as ,pieces of mica, over the end turns and winding several turns of wire such as steel or Phosphor bronze over the insulation. Balancing weights are soldered to the exterior of the band. This arrangement, although widely used, has certain disadvantages. The process of applying the insulation is time consuming and the mica used is expensive. Additionally, as successive turns of the wire are wound, the previously applied turns tend to loosen so that rerolling is often required to equalize the tension in theturns. Failure of a single turn causes failure of the entire band and probable damage to the machine.

In recent years, so called glass tape has become available commercially. Such tape comprises long glass fibers held in a binder such as a polyester or an epoxy resin. The tape has high tensile and dielectric strengths and is available in long lengths in various widths from /s to 1" with a typical thickness of about 0.015. As obtained from the manufacturer, the binder is in a semi-cured condition, feels slightly tacky to the touch, and adheres to itself sufiiciently so that a tight band can be wound. The tape may be cured by a heat treatment, typically by baking in an ovenat a temperature ofabout 150 centigrade for several hours. During the baking, the binder first flows and then solidifies into a permanentlyhard, strong mass. The semi-cured tape is obtainable from several sources including Chicago Printed String Co., Chicago, Ill., and Minnesota Mining and Manufacturing Co., St. Paul, Minn.

It has been proposed to use glass tape instead of wire for banding the end turns and while apparently satisfactory for resisting centrifugal force, it leaves unsolved the problem of adding balancing weights. Various attempts h'ave been made to solve this problem but as far as applicant is aware, hitherto no entirely satisfactory solution has been found.

It is a general object of the present invention to provide an improved method and means for handing the end turns of the rotor of a dynamoelectric machine.

Another object is to provide a method and means for dynamically balancing the rotor of a dynamoelectric machine.

Another object is to provide an improved method and means for handing theend turns to resist centrifugal force and simultaneously providing a base for the attachment of balancing weights.

Another object is to provide an improved banding arrangement which is inexpensive and easy to manufacture.

Briefly stated, a preferred embodiment of the invention contemplates winding semi-cured glass tape around the end turns with successive turns of the tape overlapping to 3,312,847 Patented Apr. 4, 1967 form a wide insulating layer. A thin strip of metal, such as tinned brass or tinned Phosphor bronze, not wider than the insulating layer, is wound over the insulating layer to form a cylindrical band. The strip of metal is formed with a series of apertures along each edge. Several additional turns of glass tape are wound, directly on top of each other, along each edge of the metal strip in the region of the apertures, leaving the central portion of the strip exposed. The entire rotor is heat treated to cure the tape, causing'the binder to flow through the apertures and harden into a solid mass. Finally the rotor is dynamically balanced by soldering Weights to the exposed portion of the metal strip.

For a clearer understanding of the invention reference may be made to the following detailed description and the accompanying drawing, in which:

FIGURE 1 is an elevation view, partly in section, of the rotor of a dynamoelectric machine incorporating the invention;

FIGURE 2 is a pictorial schematic view of the constructional details of a band according to the invention;

FIGURE 3 is a pictorial view of one of theelements of the invention;

FIGURE 4 is a pictorial view showing the invention during construction;

FIGURE 5 is a schematic cross-section view of the band; and

FIGURES 6, 7 and 8 are fic'ations of the invention.

Referring first to FIG. 1, the rotor of a dynamoelectric machine, indicated generally by the reference character 11, includes a shaft 12, a commutator 13, a commutator riser 14, a core 15, windings including end turns 16, an end turn support ring 17, a particular end turn 18 supported thereon, two bands 21 and 22 encircling the end turns on opposite ends of the rotor, and two balancing weights 23 and 24 fastened to the bands 21 and 22. I

Referring now to FIG. 2, which shows schematically the constructional details of the band 22, a layer 26 of semicured fibre glass tape is placed over the end turns. Successive turns of the tape preferably overlap each other so that the layer 26 comprises a double thickness of tape. Over the layer 26 is positioned a cylindrical metal band '27 formed with a row of apertures 28 along each edge. Additional layers 31 and 32 of glass tape are placed on pictorial views showing moditop of the band 27 directly over the apertures 28. Each layer preferably comprises several superimposed thicknesses of tape.

The cylindrical band 27 may conveniently be formed from a fiat strip of metal, wound around the layer 26 to form a cylinder. FIG. 3 illustrates a suitable strip of flexible metal to which solder readily adheres, such as tinned Phosphor bronze or tinned brass, with two rows of apertures 28 formed therein adjacent to opposite edges. The edges of the apertures 28. define radially extending surfaces 29 which, as will be more fully explained, aid in resisting buckling of the metal band. Thestrip 27 preferably has a thickness of about 0.010" to 0.020" and the width is preferably slightly less than that of the completed layer 26 of tape to be sure'that it overlies the layer 26 at all points and does not come in contact with the windings 16.

. The bands 21 and 22 are substantially identical and preferably each is made as described below in connection with the band 22. Starting with a long strip of semi-cured glass tape, the layer 26 is first wound. The tape as obtained from the manufacturer feels slightly tacky to the touch and sticks to itself sufficiently so that after the first turn is completed and the tape overlapped on itself a short distance, a substantial tension canbe applied to the feed end of the tape as it is being wound without danger of ing the end momentarily with a soldering iron.

slipping. The layer 26 is wound with a half lap or slightly more so that there are at least two thicknesses of tape over the end turns. This layer resists the centrifugal force on the end turns and also serves to protect the insulation of the end turns against abrasion by the metal band 27.

As the layer 26 is completed, and without releasing the tension on the feed end of the tape, one end of the metal strip 27 is inserted under the tape with the tape overlying one row of apertures as illustrated in FIG. 4. The tape andthe strip are then wound around the layer 26 together. As the first turn of the metal strip 27 is completed, the metal strip, if not already precut to the correct length, is severed so as to form a substantially complete metal cylinder. The glass tape, however, is not severed, and several additional thicknesses are wound directly on top of each other and over one row of apertures. Next, the tape is crossed over the metal strip 27 to the other side and several thicknesses, three or four usually being sufficient, are wound directly on top of each other and over the other row of apertures. The tape is next severed and the free end fastened to prevent slippage. Some brands of tape are sticky enough so that simply pressing the end down on the preceding turn is sufficient, while with other brands it is necessary to use a small amount of adhesive or to apply a little heat as by touch- The portion of the tape which was crossed over the metal band 27 from one side to the other is cut off and removed. The band 22 at this time is in the condition illustrated schematically in FIG. 2, with a central portion 34' of the cylindrical metal band exposed.

It would be possible to pre-form a cylindrical metal band, slip it over the layer 26 and then Wind the layers 31 and 32. However, the above described method of construction is preferred at present.

The band 22 is next cured by applying heat as recommended by the tape manufacturer, typically by baking the entire armature in an oven at a temperature of about 150 centigrade for several hours. The binder of the semi-cured tape first flows and then hardens. The half lapped layer 26 becomes a single hard insulating layer, sticking somewhat to the end turns 16 and conforming to the irregularities of the covering insulation. Layers 31 and 32 likewise each become a single hard mass of insulation. The binder also flows through the apertures 28, forming projections or pins 36 which. join the layers 31 and 32 to the layer 26, in effect riveting the cylindrical metal band 27 to the insulating mass, as illustrated in FIG. 5.

rotor has been baked sufficiently to cure the tape, drive out moisture, and preheat the bars, the rotor is removed from the oven and While still hot, the windings are soldered to the risers of the commutator bars. Next the rotor is impregnated with varnish, for example, by dipping, to seal the windings against moisture. The rotor is next cooled and is ready for balancing.

The rotor is tested for dynamic balance, apparatus for this purpose being well known. Typically such apparatus spins the rotor and indicates the amount and location of the masses which must be added to remove the inherent unbalance. The varnish is scraped off the designated areas of the metal bands 27 and appropriate weights are soldered thereto. Two such weights are shown at 23 and 24 of FIG. 1. If the required weights are small, solder alone may be suflicient. Solder solidifies quickly and the rotor may be checked for balance and adjustments made immediately without the necessity for waiting for cement to set as is necessary in some proposed methods of attaching weights.

The balancing weights are fastened to the metal band 27 and when the machine rotates, centrifugal force tends 4. to buckle the band 27 at the center, tending to withdraw the edges toward the center. This tendency is resisted by the pin portions 36 of the cured tape which cooperate with the radially extending surfaces 29 defined by the apertures 28. If the metal band 27 were made thick enough, it would be possible to omit the apertures 28 and simply wind the layers 31 and 32 over the edges of the band, but at present the arrangement described including the apertures 28 is preferred.

Usually the surface of the end turns is generally cylindrical and a metal strip 27 as illustrated in FIG. 3 is suitable. However, if the end turns have a generally conical surface, a strip 41 as illustrated in FIG. 6 may be used. A number of slots 42 are cut in one edge to allow the strip to conform to a conical surface. If the end turn surface is irregular, a strip 44 as illustrated in FIG. 7 may be used. This strip has slots 45 in one edge and slots 46 in the otheredge to aid in winding the strip over an irregular surface.

FIGURE 8 illustrates a modified form of the metal band. In this form, a metal strip denoted generally by the reference character 51 is formed with upstanding ridges 52 and 53 along each edge and with similar ridges 54 and 55 intermediate the edges. The distance between the ridges 52 and 54 and between the ridges 53 and 55 is made approximately equal to the width of the tape used and the layers 31 and 32 are wound between these ridges as shown. When the strip 51 is Wound around the end turns to form a cylindrical band, the ridges comprise radially extending surfaces which cooperate with the layers 31 and 32 to resist axial sifting of the band 51 and also to resist buckling due to centrifugal force when weights are soldered to the exposed central portion 56. It will be understood that FIG. 8 is a schematic showing and that the thickness of the strip and the height of the ridges are shown exaggerated.

From the foregoing description it is apparent that the present invention provides a banding arrangement with many advantages. The bands are easily applied and of ample strength to resist the centrifugal force of both the end turns and of the balancing weights. The tape is cured during the regular baking process so that no extra time is required. Since the balancing weights are fastened by soldering, the rotor can be checked for balance without waiting for any cement to set.

Although a specific embodiment of the invention has been described in considerable detail for illustrative purposes, many modifications will occur to those skilled in the art. It is therefore desired that the protection afforded by Letters Patent be limited only by the true scope of the appended claims.

I claim:

1. The method of banding the end turns of a dy-' namoelectric machine comprising the steps of wrapping a first layer of semi-cured tape around said end turns,

applying a layer of metal over said first layer of tape to form a metal band,

wrapping two additional layers of semi-cured tape around said metal band and said first layer, one adjacent to each edge of said metal band, leaving a central portion of said metal band exposed, and

applying heat to said layers to cure said tape.

2. The method of banding the end turns of a dynamoelectric machine comprising the steps of wrapping a first layer of semi-cured insulating tape around said end turns,

wrapping a strip of metal formed with apertures adjacent each edge over said first layer to form a cylindrical metal band,

wrapping two additional layers of semi-cured tape around said metal band, one layer over the apertures adjacent to each edge, leaving a central portion of said band exposed, and

applying heat to said layers to cure said tape.

3. The method of handing the end turns of a dynamoelectric machine comprising the steps of a dynamoelectric machine having end turns projecting from slots in the core member thereof comprising the steps of wrapping a first layer of semi-cured insulating tape around said end turns,

wrapping a strip of metal over said first layer to form a gneerally cylindrical metal band,

wrapping two additional layers of semi-cured tape around said metal band, one adjacent to each edge of said band, leaving a central portion of said band exposed,

applying heat to said layers to cure said tape,

testing said rotor in a balancing machine to discover the magnitude and location of unbalance, and

fastening weights to said exposed surface to compensate for the discovered unbalance.

5. The method of claim 4 in which said weights are fastened by soldering.

6. The method of banding the end turns of the rotor of a dynamoelectric machine comprising the steps of winding a plurality of axially overlapping turns of semi-cured fibre glass tape around said end turns to form an insulating layer,

without severing said tape, inserting one end of a rectangular strip of metal, of width no greater than said layer over said layer and under the feed portion of said tape,

winding said strip and said tape simultaneously over said layer to form a cylindrical metal band overlaid near one edge with a layer of tape,

crossing said glass tape over the central portion of said metal band to the vicinity of the other edge thereof,

winding an additional layer of glass tape over said band near said other edge,

severing said tape upon completion of the last named layer,

removing the portion of said tape overlying the central portion of said metal band, and

applying heat to said layers to cure said tape to a permanently hard rigid mass.

7. The method of banding the end turns of the rotor of a dynamoelectric machine comprising the steps of winding a plurality of axially overlapping turns of semi-cured fibre glass tape around said end turn to form an insulating layer, without severing said tape, inserting one end of a rectangular strip of metal, of width no greater than that of said layer, and having formed therein two rows of apertures one adjacent to each edge thereof, over said layer with one row of apertures under the feed portion of said tape, said strip having a length substantially equal to the circumference of 7 said layer,

winding said strip and said tape simultaneously around said layer to form a cylindrical metal band overlaid in the region of one row of apertures with a layer of tape,

crossing said tape over the central portion of said metal band to the vicinity of the other row of apertures,

winding an additional layer of tape over said other row of apertures,

severing said tape upon completion of the last named layer of tape,

removing the portion of said tape overlying the central portion of said metal band when said tape was crossed over, and

applying heat to said layers of tape causing the binder in said tape first to flow and then to harden, whereby said insulating layer of tape is joined to the overlying layers through pin portions extending through the apertures in said metal band.

8. Banding apparatus for the end turns of the rotor of a dynamoelectric machine, comprising of insulating material comprise cured fibre glass tape.

10. Banding and balancing apparatus for the rotor of a dynamoelectric machine which includes end turns projecting from the core thereof, comprising,

a layer of insulating material encircling said end turns,

a cylindrical metal band encircling said layer,

first and second additional layers of insulating material, each substantially narrower than said metal band, encircling said band adjacent to opposite edges thereof leaving exposed a portion of said band between said additional layers,

said layers of insulating material being in the form of a hard, solid mass, and

a balancing weight fastened to said exposed portion of said band.

11. Apparatus according to claim 10 in which said metal 'band is formed with radially extending surfaces.

12. Banding apparatus for the end turns of the rotor of a dynamoelectric machine, comprising,

a first layer of insulating material tightly encircling said end turns,

a cylindrical metal band, having a width not greater than that of said first layer, tightly encircling said first layer,

said band being formed with a plurality of apertures adjacent to each edge,

second and third layers of insulating material, each substantially narrower than said metal band, tightly encircling said band adjacent to opposite edges thereof over said apertures leaving exposed a portion of said band between said second and third layers, and

a plurality of pin portions of insulating material extending through said apertures,

said layers and said pin portions being in the form of a single solid mass.

13. Apparatus according to claim 12 in which said 14. Banding and balancing apparatus for the rotor of a dynamoelectric machine which includes end turns projecting from slots in the core thereof, comprising,

a first layer of insulating material tightly encircling said end turns,

a generally cylindrical metal band, having a width not greater than that of said first layer, tightly encircling said first layer,

said band being formed with a row of apertures adjacent to each edge,

second and third layers of insulating material, each substantially narrower than said metal band, tightly encircling said band adjacent to opposite edges thereof over said apertures leaving exposed a central portion of said band between said second and third layers,

a plurality of pin portions of insulating material extending through said apertures,

said layers and said pin portions being in the form of a single solid mass, and

a balancing weight fastened to said central portion of said metal band,

15. Apparatus according to claim 14 in which said layers of insulating material comprise cured fibre glass tape and said pin portions are formed by the flow and solidification of the binder of said tape during the curing thereof.

16. A band encircling the end turns of windings projecting from slots in the core member of the rotor of a dynamoelectric machine, said band comprising,

a rigid mass of insulating material of. a generally cylindrical shape,

said mass including a first cylindrical portion of generally rectangular cross section in engagement with said end turns,

a cylindrical metal band, having a width no greater than the width of said first portion, encircling said first portion,

said metal band being formed with two rows of apertures, one adjacent to each edge thereof,

said mass also including second and third cylindrical portions, each of generally rectangular cross section, each narrower than said first portion, and each overlying said metal band, one in the region of each of said series of apertures,

said mass also including a plurality of radially extending pin portions integral with and joining said first portion to said second and third portions through said aperturesin said metal band.

i No references cited.

MILTON O. HIRSHFIELD, Primary Examiner.

J. W. GIBBS, Assistant Examiner. I 

8. BANDING APPARATUS FOR THE END TURNS OF THE ROTOR OF A DYNAMOELECTRIC MACHINE, COMPRISING A LAYER OF INSULATING MATERIAL TIGHTLY ENCIRCLING SAID END TURNS, A CYLINDRICAL METALLIC BAND, HAVING A WIDTH NOT GREATER THAN THAT OF SAID LAYER, TIGHTLY ENCIRCLING SAID LAYER, AND FIRST AND SECOND ADDITIONAL LAYERS OF INSULATING MATERIAL, EACH SUBSTANTIALLY NARROWER THAN SAID METAL BAND, TIGHTLY ENCIRCLING SAID BAND ADJACENT TO OPPOSITE EDGES THEREOF LEAVING EXPOSED A PORTION OF SAID BAND BETWEEN SAID ADDITIONAL LAYERS, SAID LAYERS OF INSULATING MATERIAL BEING IN THE FORM OF HARD, SOLID MASSES. 